Removing Dirt From Limestone Ornament Using A Hot Lime Poultice

Procedure code:

446001S

Source:

Developed For Hspg (Nps - Sero)

Division:

Masonry

Section:

Limestone

Last Modified:

02/24/2012

REMOVING DIRT FROM LIMESTONE ORNAMENT
USING A HOT LIME POULTICE

THE CLEANING OR REMOVAL OF STAINS FROM STONE MAY INVOLVE THE USE
OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON ADJACENT
MATERIAL, DISCOLOR THE STONE OR DRIVE THE STAINS DEEPER INTO POROUS
STONES. USE THE PRODUCTS AND TECHNIQUES DESCRIBED HERE ONLY FOR
THE COMBINATIONS OF DIRT/STAIN AND STONE SPECIFIED.

PART 1---GENERAL

1.01 SUMMARY

A. This procedure includes guidance on cleaning dirt
from
limestone using a hot lime poultice
- also known as
Baker's Lime Method. Developed
by Robert Baker in the
1950's, THIS METHOD OF DIRT REMOVAL
IS LABOR INTENSIVE
AND, THEREFORE, IS BEST USED ON HIGHLY
SIGNIFICANT
ARCHITECTURAL DETAILS.

1. Baker's Lime Method is a 4-stage
process which
includes cleaning, repair,
consolidating and
preserving.

2. This procedure describes the
cleaning stage. Other
stages in the process
are described in 04460-02-R.

B. Dirt may consist of particles of dust, sand or
grit, or
tarry soot. Particulate dirt or
soiling may result from
vehicular or human traffic or from pollutant
or sulfate
crusts building up in protected areas
not regularly
washed by rain. Pollutant crusts
hasten masonry
dissolution and should be removed.

C. Safety Precautions: Check manufacturer's literature
for
precautions and effects of products
and procedures on
adjacent building materials, components,
and especially
vegetation. Take appropriate protective
measures.

D. See 01100-07-S for general project guidelines
to be
reviewed along with this procedure.
These guidelines
cover the following sections:

1. Safety Precautions

2. Historic Structures Precautions

3. Submittals

4. Quality Assurance

5. Delivery, Storage and Handling

6. Project/Site Conditions

7. Sequencing and Scheduling

8. General Protection (Surface
and Surrounding)

These guidelines should be reviewed
prior to performing
this procedure and should be followed,
when applicable,
along with recommendations from the
Regional Historic
Preservation Officer (RHPO).

E. For general information on the characteristics,
uses and
problems associated with limestone,
see 04460-01-S.

PART 2---PRODUCTS

2.01 MATERIALS

A. Lime putty

B. Burlap or cheesecloth

C. Plastic sheeting

D. String

E. Clean potable water

2.02 EQUIPMENT

A. Hand spray bottle

B. Dental picks

C. Small, soft bristle brushes

D. Trowels and spatulas

PART 3---EXECUTION

3.01 ERECTION/INSTALLATION/APPLICATION

A. Thoroughly wet the stone with clean water.

B. Using a trowel, press lime putty into the affected
limestone ornament.

C. After a thick coat has been applied, bind it with
wet
burlap or cheesecloth; Secure it with
string.

D. Loosely tie a heavy-duty polyethylene sheet around
the
ornament.

E. Keep the ornament covered for about 2-3 weeks.

F. Periodically, lift the sacking during that time
and spray
the poultice with water to keep the
poultice damp.

G. Carefully lift off the lime in small portions
using
spatulas or small trowels (use water
sprays to help
loosen the poultice).

H. Much of the dirt will not immediately detach with
the
poultice material; The poultice moistens
the dirt so that
it can be removed more easily by washing
and brushing.